Wide‐Gap Chalcopyrite Solar Cells with Indium Oxide–Based Transparent Back Contacts

Herein, the performance of wide-gap Cu(In,Ga)Se2 (CIGS) and (Ag,Cu)(In,Ga)Se2 (ACIGS) solar cells with In2O3:Sn (ITO) In2O3:H (IOH) as transparent back contact (TBC) materials is evaluated. Since both TBCs restrict sodium in-diffusion from glass substrate, fine-tuning a NaF precursor layer crucial. It found that optimum Na supply lower for ACIGS than CIGS samples. An excessive amount deteriorates cell performance, presumably by facilitating GaO x growth at TBC/absorber interface. The efficiency (η) further depends on absorber stoichiometry, highest fill factors (and η) reached close-stoichiometric compositions. η = 12% bandgap 1.44 eV processed, using IOH TBC. best device reaches 11.2% ITO. Due to its very high infrared transparency, judged superior ITO implementation in top tandem device. However, while layers maintain their conductivity, films show an increased sheet resistance after deposition. Chemical investigations indicate incorporation Se during initial stage processing may be responsible deteriorated conductivity final